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The Global ETD Search service is a free service for researchers
to find electronic theses and dissertations. This service is
provided by the
Networked Digital Library of Theses and Dissertations.
Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
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Regulation of branching by phytochrome B and PPFD in Arabidopsis thalianaChou, Nan-yen 10 October 2008 (has links)
The branching or tillering of crops is an important agronomic trait with a major
impact on yield. Maintaining an appropriate number of branches allows the plant to use
limited light resources and to produce biomass or yield more effectively. The branching
process includes the initiation of the axillary meristem leading to bud formation and the
further outgrowth of the axillary buds. Phytohormones, including cytokinins and auxin,
are known to play major roles in regulating axillary bud outgrowth.
Light signals, including light quantity and light quality, are among the most
important factors regulating plant growth and are perceived by the action of specialized
photoreceptors, including phytochromes. Phytochromes sense red (R) and far-red (FR)
light and allow some plants to perceive and respond to competing neighbors by evoking
the shade avoidance syndrome (SAS). One component of the SAS is inhibition of
branching. Phytochrome B (phyB) is especially important in sensing shade signals and
loss of phyB function results in a constitutive shade avoidance phenotype, including
reduced branching. While it has been anecdotally reported that phyB-deficient
Arabidopsis branches less than wild type, a detailed study of the defects in the process is
lacking. In this research, the interactions between light signals, phytochromes and phytohormones in the regulation of branching were assessed using an integrated
physiological, molecular and genetic approach.
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Cotton Response to 1-Methylcyclopropene Under Different Light Regimes and Growth Stages: Lint Yield and Yield ComponentsCarden, Charles Warren 2010 August 1900 (has links)
Low photosynthetic photon flux density (PPFD) during certain growth periods of cotton (Gossypium hirsutum L.) has been shown to impact yield, ethylene synthesis, and fiber quality. Previous research with shading has shown that lint yield can be significantly reduced in the latter stages of growth. This two-year field study was conducted at the Texas A&M AgriLife Research Farm in Burleson County, Texas, in 2008 and 2009. The study evaluated the impact of an 8-day period of shade (63 percent reduction of PPFD) on cotton yield parameters, fiber quality, and the impact of 1-methylcyclopropene (1-MCP), an ethylene inhibitor, to alter detrimental cotton responses when applied as a foliar spray under shaded and non-shaded conditions. Shade and 1-MCP were imposed at four developmental stages of growth: pinhead square (PHS), first flower (FF), peak flower (PF), and boll development (BD). Data pooled over both years indicated that there were no significant differences in yield for 1-MCP treatments; however, numerical differences existed. Shade applied during the BD stage of development showed significantly lower yield than the untreated control. These results showed a decline in seed cotton and ginned seed cotton by 522 and 207 kg ha-1, respectively. To further analyze further yield components, box-mapping was conducted during both years. However, this data failed to explain consistent patterns of the observed yield responses. Data was also collected to determine the amount of fibers per seed and seed weights. Cotton fiber data did not show consistent correlations with the numerical increases and significant decreases in yield. Electrolyte leakage and stomatal conductance data also were collected. Electrolyte leakage showed no statistical differences when compared to the untreated control. Stomatal conductance measurements showed no consistency for treatments during both years.
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Hypsometrischer Klima- und Bodenwandel in Bergregenwaldökosystemen Boliviens / Altitudinal change of climate and soils in Bolivian tropical montane rainforest ecosystemsSchawe, Marcus 06 July 2005 (has links)
No description available.
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Relationships between soil chemical properties and forest structure, productivity and floristic diversity along an altitudinal transect of moist tropical forest in Amazonia, Ecuador. / Beziehungen zwischen bodenchemischen Eigenschaften und Waldstruktur, Produktivität und floristischer Diversität tropischer Regenwälder Amazoniens entlang eines Höhengradienten in Ecuador.Unger, Malte Arne 30 April 2010 (has links)
No description available.
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